Antimicrobial Effect of Postbiotics on Multidrug-Resistant Escherichia coli

Pathogens that have developed resistance to antibiotics pose a threat to public health. The primary goal in preventing foodborne infections is to inhibit the growth of and, subsequently, eliminate antibiotic-resistant pathogens at every stage from production to consumption. Escherichia coli, which has acquired resistance to most known antibiotics, is frequently found in chicken meat. In many countries, due to unregulated antibiotic use in poultry farming, poor hygiene in slaughterhouses, or cross-contamination, extended-spectrum beta-lactamase (ESBL)-producing <i>E. coli</i> has been identified as the causative agent in poultry-associated food poisoning. The need for more effective antimicrobial agents against this pathogen, which is resistant to existing antibiotics, has led to increased attention being paid to postbiotics produced by lactic acid bacteria, particularly bacteriocins. This study aimed to determine the antimicrobial effects of postbiotics obtained from kefir-derived <i>Lactiplantibacillus plantarum</i> and <i>Lactococcus lactis</i> against ESBL-positive <i>E. coli</i>. To achieve this, <i>E. coli</i> strains were isolated from raw chicken meat samples collected from the market using culture-based methods, and their antimicrobial resistance profiles were determined using the disk diffusion method. The ESBL positivity of the isolates was assessed using the double-disk synergy test. The antimicrobial activities of the postbiotics against the identified ESBL-positive <i>E. coli</i> strains were tested using the macro-dilution method to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. ESBL-positive <i>E. coli</i> was detected in 48% of raw chicken meat samples. The antimicrobial effects of postbiotics were examined by disk diffusion, and postbiotics produced by 18 <i>Lb. plantarum</i> strains and 20 <i>Lc. lactis</i> strains showed strong antimicrobial activity. Significant differences in the antimicrobial effects of postbiotics were observed between the two species. <i>Lb. plantarum</i> postbiotics exhibited both bacteriostatic (concentration 60%) and bactericidal (concentration 80%) effects on ESBL-positive <i>E. coli</i> strains, whereas <i>Lc. lactis</i> postbiotics showed only bacteriostatic effects (80% concentration). Postbiotics derived from probiotic bacteria offer promising effects against multidrug-resistant <i>E. coli</i> due to their heat resistance, activity across different pH values, strong antimicrobial effects, affordability, and ease of production.